Metal single atom (MSA) materials exhibit excellent properties and are receiving widespread interest for their effectiveness in promoting a variety of catalytic reactions. The current strategies for preparing MSA catalysts involve complicated operation flows and suffer from low loading of the single atoms prepared, owing to the surface defect density of the substrate. In this paper, we report a simple physical method for preparing high-density copper single atom catalysts on amorphous carbon by Coulomb explosion. The results of the in situ observation showed that copper atoms on particle surfaces were emitted under electron beam irradiation and were captured by defects in a surrounding amorphous carbon film as isolated single atoms. By controlling the time and intensity of the Coulomb explosion, the ratio of copper single atoms to clusters aggregated from single atoms on the amorphous carbon can be controlled. Our work will provide new ideas for a universal simple physical preparation of MSA catalysts.